The stone walls, square moat, and foundations of the tenshu tower that remain today are from this renovation.

Therefore, during the Shimabara Rebellion from 1637 to 1638, rebels were able to successfully barricade themselves in the abandoned Hara Castle for many months against the forces of the Tokugawa shogunate.

After the Shimabara Rebellion, the shogunate demolished the stone walls and other structures remaining at the site of the castle.

[2] During various archaeological excavations on the site, the remains of rebels who either fell in battle or were executed afterwards, lead bullets, rosaries and crucifixes were unearthed.

[3] On June 30, 2018 Hara Castle along with 11 other sites linked to Catholic persecution in Japan, was added to the UNESCO World Heritage List.